Ditylenchus gallaeformans sp. n. (Tylenchida: Anguinidae) – a neotropical nematode with biocontrol potential against weedy Melastomataceae

<jats:p><jats:italic>Ditylenchus gallaeformans</jats:italic> sp. n. was found on several hosts at numerous locations in Brazil and Costa Rica. In its native habitats it attacks several genera in the Melastomataceae, including two species ranked as among the worst invasive weeds of Pacific island forests, namely <jats:italic>Miconia calvescens</jats:italic> and <jats:italic>Clidemia hirta</jats:italic>. The new species causes a severe disease on infected plants involving the formation of gall-like structures on infected leaves, inflorescences and stems, and may cause significant impact on its hosts. Morphological study using light and scanning electron microscopy and analysis of the partial 18S rRNA, the D2-D3 expansion fragments of 28S rRNA and the ITS rRNA gene sequences showed little variations between populations from different hosts or geographical origins. The molecular study revealed that the new species is related to <jats:italic>D. drepanocercus</jats:italic>, which was recently found in association with <jats:italic>M. calvescens</jats:italic> but causing angular leaf spots on this host. <jats:italic>Ditylenchus gallaeformans</jats:italic> sp. n. is distinguished from <jats:italic>D. drepanocercus</jats:italic> by having a bursa reaching the tail tip (<jats:italic>vs</jats:italic> covering around 50% of tail in <jats:italic>D. drepanocercus</jats:italic>) and a conical tail, regularly tapering towards a variable tip (<jats:italic>vs</jats:italic> tail with a distinctive apical falciform appendage in both sexes in <jats:italic>D. drepanocercus</jats:italic>). PCR with species-specific primers was developed for diagnostics of both <jats:italic>Ditylenchus</jats:italic> species. <jats:italic>Ditylenchus gallaeformans</jats:italic> sp. n. deserves further investigation as a potential biocontrol agent against <jats:italic>M. calvescens</jats:italic> and <jats:italic>C. hirta</jats:italic>.</jats:p>